In the course of being side-tracked while helping to do some research for yesterday's show, I learned that the above is called a Beam Splice Moment Connection.
Moment connection? Like eyes that meet across the subway platform?
Moment is a mechanical engineer's word for torque, although it has a little bit different meaning in the mechanical context. Cribbing from Wikipedia:
The definition of torque states that one or both of the angular velocity or the moment of inertia of an object are changing. And moment is the general term used for the tendency of one or more applied forces to rotate an object about an axis, but not necessarily to change the angular momentum of the object (the concept which in physics is called torque).
So the joint above is meant to secure two beams against twisting forces.
Forces acting to twist or turn an object are called a couple. A couple, even a "simple couple" of just two forces, produces a* "pure moment." And so two beams are joined at a moment connection to resist the tendency of a couple to turn them through a pure moment.
Does this sound as romantic to those of you who actually use these terms on a regular basis as it does to me?
*Is it "a" pure moment or just pure moment? The way moment, torque and couple are used to define each other makes it hard for the layman to break in.